The present invention relates to refrigeration systems, and more particularly, to a manifold gauge set assembly for use in charging a refrigerant into a refrigeration system at start-up or during a service condition.
Manifold gauge sets are utilized by air conditioning and refrigeration technicians to service and/or charge the equipment that comprises the air conditioning or refrigeration system. A manifold gauge set provides readout devices from which the operational (i.e., discharge and suction) pressures of the system can be determined, and provides one or more ports through which the technician can charge refrigerant from a storage cylinder into the system.
New air conditioning and refrigeration systems must be fully charged with refrigerant prior to first use of the system. In addition, existing systems from time to time require the addition of refrigerant to re-charge or top off a system due to the leakage of refrigerant from the system. When a refrigerant is to be charged into a refrigeration system, either as part of a new installation or as part of a service operation (top off), the refrigerant is typically charged into the system through a manifold gauge set. In a typical charging operation, the service technician pulls a vacuum through the gauge set on the system, and thereafter charges liquid refrigerant from the cylinder through the manifold gauge set and into the high side (also known as the liquid side) of the system.
As liquid refrigerant is charged into the system as part of a charging operation, the pressure in the high side gradually increases. If the pressure in the high side increases to an extent that it reaches the pressure inside the tank, the flow of liquid refrigerant ceases, and additional liquid refrigerant can no longer be introduced into the high side. In this event, the remaining portion of the refrigerant charge must be added to the low side (also known as the suction side) of the system in a vapor state.
It is well known in the refrigeration art that the removal of refrigerant vapor from a cylinder causes heat to be removed along with the vapor. As the temperature in the cylinder drops due to the removal of the heat with the vapor, the pressure in the cylinder also drops. As a consequence of this pressure drop, the rate of transfer of the vapor from the cylinder to the refrigeration system is reduced, ultimately to a point that the transfer becomes almost nonexistent. In order to increase the charge rate, and thereby more rapidly complete the charging operation, a service technician may attempt to circumvent the temperature/pressure loss in the cylinder by slowly introducing liquid (rather than vapor) from the cylinder into the low (suction) side of the system. Since the compressor can only compress low pressure vapor to high pressure vapor, the charging of liquid refrigerant into the low side can severely damage or even destroy the compressor. Such action can also result in harm to the technician due to the malfunction of the compressor.
The hazards associated with introducing liquid refrigerant directly into the low side of the compressor may be avoided when the technician utilizes a refrigerant phase change device. Applying Bernoulli""s Principle (as the speed of a moving fluid increases, the pressure within the fluid decreases) to a volatile refrigerant allows for the expansion of the refrigerant with the drop in pressure and a change of state. Further application of the principle as described as the venturi effect is represented with different embodiments of the present invention.
Refrigerant phase change devices of this type are used to withdraw liquid refrigerant from the cylinder, rather than refrigerant vapor, for charging into the low side of the system. After being withdrawn from the cylinder, the liquid refrigerant passes through one or more pressure drop baffles, orifices or other restrictions in the phase change device, and is ultimately converted (flashed) to the vapor phase as it leaves the device and is charged into the low side of the system.
Since the early 1990""s, in concert with the Montreal Protocol and the pending ban on CFC refrigerants, substitute or alternative refrigerants were developed to replace the refrigerants that were banned, or that were scheduled to be banned. With the exception of two single molecule refrigerants introduced for permanent inclusion in the industry, the remaining alternatives were classified as blends, which blends are zeotropic in nature.
Phase change devices as described are also utilized when the refrigerant composition to be charged into the system comprises a blend of refrigerants (i.e., a zeotrope), rather than a pure refrigerant. The individual components in a zeotrope boil, or change phase, at different temperatures, thereby causing the composition of the refrigerant blend to change at each component""s respective boiling point. If a refrigerant composition comprising a blend of refrigerant components is charged into the system as a vapor, then the vapor will include an incorrect percentage of the various components of the liquid blend. In particular, the vapor charged into the system will generally comprise a higher percentage of the most volatile components than of the least volatile components. As a result, the true composition of the charged refrigerant will be altered from the intended composition, thereby hindering the charged system from performing as intended.
In addition, if refrigerant vapor enriched with one or more of the most volatile components is removed from the cylinder, the blend of refrigerants remaining in the cylinder will no longer include the proper percentages of each of the individual components. The use of the phase change device allows the technician to charge the refrigerant blend from the cylinder as a liquid, rather than as a vapor, thereby maintaining the proper percentages of the components of the refrigerant blend. Since multiple systems may be charged from a single cylinder of refrigerant, a cylinder having a compromised percentage composition could damage many systems and cause adverse economic consequences.
Although the benefits of using a phase change device are well known, the use of such devices can be inconvenient to a service technician. For example, as an initial matter, the device must be readily accessible to the technician, a feat that is not always accomplished when working at a remote site. The technician must then isolate the suction service access port, allowing removal of the suction side service hose from the manifold gauge set. This process will, as a result of this action, cause a slight expulsion of refrigerant trapped in the hose to the atmosphere as a consequence. The phase change device is installed at the suction hose connection port of the manifold gauge set, and the service hose is attached to the opposite side of the phase change device. The manifold gauge set suction side is opened allowing refrigerant to fill the hose, and the hose fitting is loosened at the system suction connection to purge any refrigerant and non-condensables to the atmosphere.
In an alternative arrangement, the center (or common) charging hose of the manifold gauge set is removed from the cylinder, resulting in the expulsion of refrigerant trapped in the hose to the atmosphere. The phase change device is secured to the refrigerant cylinder, and the center hose is attached to the phase change device. The cylinder valve is opened allowing refrigerant to fill the hose, and the hose fitting is loosened at the manifold gauge set to purge any refrigerant and non-condensable to the atmosphere. In the event the technician requires an unimpeded flow of refrigerant, then the process must be reversed to remove the phase change device from the cylinder.
The actions described above slow the operation, and require that the technician possess the proper equipment for introducing the device into the system.
It would be preferable if a charging operation could be carried out in a more efficient manner than is presently possible, by combining in a charging apparatus the benefits of a phase change device with the existing equipment of the system. Such a device should be sufficiently versatile such that a system evacuation (pulling a vacuum) and charging operation could be readily completed regardless of whether liquid refrigerant is being charged into the high or low side of the system, and without requiring the technician to connect or disconnect auxiliary devices after the charging operation has commenced and eliminate unnecessary multiple expulsions of refrigerant to the atmosphere.
The present invention overcomes the disadvantages present in charging operations by providing an improved manifold gauge assembly that combines in a single apparatus the features of a manifold gauge set and the features of a phase change device. Also included is an alternative phase change device that is adapted to be permanently affixed to an existing manifold gauge set to provide a device offering the same benefits as the integral apparatus.
The improved manifold gauge assembly may be utilized for charging both pure liquid refrigerants and blends of liquid refrigerants and still maintain the ability of full porting for vacuum optimization. Since the features of the manifold and the phase change device are combined, a technician may withdraw liquid refrigerant from a cylinder for charging into either the high side (as a liquid) or the low side (as a vapor resulting from phase conversion) of the system without the necessity of interrupting a charging operation for installation or elimination of equipment. The invention also comprises an improved phase change device adapted for fixed attachment with a manifold.